CN113777721A

CN113777721A - Optical module

Info

Publication number: CN113777721A
Application number: CN202010524474.1A
Authority: CN
Inventors: 陈思涛; 隋少帅; 尹延龙; 赵其圣
Original assignee: Hisense Broadband Multimedia Technology Co Ltd
Current assignee: Hisense Broadband Multimedia Technology Co Ltd
Priority date: 2020-06-10
Filing date: 2020-06-10
Publication date: 2021-12-10
Anticipated expiration: 2040-06-10
Also published as: CN113777721B

Abstract

The application discloses an optical module, which comprises a circuit board, a light source and a silicon optical chip, wherein the silicon optical chip comprises a silicon optical modulator, the silicon optical modulator comprises a traveling wave electrode arranged in a bent mode and a silicon optical waveguide arranged in a bent mode, and the projection of the silicon optical waveguide on the traveling wave electrode is located between a ground wire and a signal wire; the traveling wave electrode comprises a first section of traveling wave electrode, a bent section of traveling wave electrode and a second section of traveling wave electrode, and the first section of traveling wave electrode and the second section of traveling wave electrode are symmetrically arranged; the silicon optical waveguide comprises a first section of PN junction silicon optical waveguide, a bent section of silicon optical waveguide and a second section of PN junction silicon optical waveguide, the first section of PN junction silicon optical waveguide is electrically connected with a first ground wire and a signal wire of the first section of traveling wave electrode, and the second section of PN junction silicon optical waveguide is electrically connected with the signal wire and a second ground wire of the second section of traveling wave electrode. The bending traveling wave electrode and the silicon optical waveguide are arranged in a crossed mode, so that an equivalent symmetrical PN junction load is realized, the generation of a high-order radio frequency mode is effectively inhibited, and the signal transmission quality is improved.

Description

Optical module

Technical Field

The application relates to the technical field of optical communication, in particular to an optical module.

Background

The optical communication technology is used in new services and application modes such as cloud computing, mobile internet, video and the like, and in optical communication, an optical module is a tool for realizing the interconversion of photoelectric signals and is one of key devices in optical communication equipment. The adoption of a silicon optical chip to realize a photoelectric conversion function has become a mainstream scheme adopted by a high-speed optical module.

In the silicon optical module, a silicon optical chip comprises a silicon optical modulator, an optical carrier signal emitted by a laser enters the silicon optical modulator, and a high-speed data stream is loaded on the optical carrier signal in a driving voltage mode to complete the modulation of light. The traditional silicon optical modulator adopts a linear traveling wave electrode design to realize high-speed electro-optical modulation, the common traveling wave electrode adopts a coplanar waveguide type transmission line GSG structure, S is a signal line and is positioned in the middle, and G is a ground wire and is positioned at two sides of the S signal line. The silicon optical waveguide forms a PN junction through doping, and the PN junction is used as a load of the GSG traveling wave electrode to realize electro-optic response.

However, the silicon optical waveguide prepared into the PN junction is usually a linear optical waveguide, and therefore, the silicon optical waveguide can only be connected with one group of GS signal lines, and the other G ground line is in a suspended state, so that asymmetry of the whole system is caused, and a GSG traveling wave electrode generates a high-order radio frequency mode, which affects signal transmission quality.

Disclosure of Invention

The application provides an optical module to solve the problem that the signal transmission quality of a linear traveling wave electrode in the existing silicon optical modulator is poor.

In order to solve the technical problem, the embodiment of the application discloses the following technical scheme:

the embodiment of the application discloses an optical module, includes:

a circuit board;

the light source is electrically connected with the circuit board and is used for emitting light which does not carry signals;

the silicon optical chip is electrically connected with the circuit board and comprises a silicon optical modulator, the light which is emitted by the light source and does not carry signals is received through an input optical port of the silicon optical chip, the silicon optical modulator modulates the light which does not carry signals into signal light and outputs the signal light through an output optical port of the silicon optical chip;

the silicon optical modulator comprises an interference arm, the interference arm comprises a traveling wave electrode arranged in a bent mode and a silicon optical waveguide arranged in a bent mode, and the projection of the silicon optical waveguide on the traveling wave electrode is located between a ground wire and a signal wire;

the traveling wave electrode comprises a first section of traveling wave electrode, a bent section of traveling wave electrode and a second section of traveling wave electrode which are integrally connected, and the first section of traveling wave electrode and the second section of traveling wave electrode are symmetrically arranged;

the silicon optical waveguide comprises a first section of PN junction silicon optical waveguide, a bent section of silicon optical waveguide and a second section of PN junction silicon optical waveguide, the projection of the first section of PN junction silicon optical waveguide on the traveling wave electrode is positioned between a first ground wire and a signal wire of the first section of traveling wave electrode, and the PN junction of the first section of PN junction silicon optical waveguide is respectively and electrically connected with the first ground wire and the signal wire; the projection of the second section of the PN junction silicon optical waveguide on the traveling wave electrode is positioned between a signal line and a second ground of the second section of the traveling wave electrode, and the PN junction of the second section of the PN junction silicon optical waveguide is electrically connected with the signal line and the second ground respectively; and the signal line of the traveling wave electrode is electrically connected with the P-type semiconductor of the first section of PN junction silicon optical waveguide and the P-type semiconductor of the second section of PN junction silicon optical waveguide respectively, or the signal line is electrically connected with the N-type semiconductor of the first section of PN junction silicon optical waveguide and the N-type semiconductor of the second section of PN junction silicon optical waveguide respectively.

The optical module comprises a circuit board, a light source and a silicon optical chip, wherein the silicon optical chip comprises a silicon optical modulator, the silicon optical modulator comprises an interference arm, the interference arm comprises a traveling wave electrode arranged in a bent mode and a silicon optical waveguide arranged in a bent mode, and the silicon optical waveguide is arranged between a ground wire and a signal wire of the traveling wave electrode; the traveling wave electrode comprises a first section of traveling wave electrode, a bent section of traveling wave electrode and a second section of traveling wave electrode which are integrally connected, and the first section of traveling wave electrode and the second section of traveling wave electrode are symmetrically arranged; the silicon optical waveguide comprises a first section of PN junction silicon optical waveguide, a bent section of silicon optical waveguide and a second section of PN junction silicon optical waveguide, the projection of the first section of PN junction silicon optical waveguide on the traveling wave electrode is positioned between a first ground wire and a signal wire of the first section of traveling wave electrode, and the PN junction of the first section of PN junction silicon optical waveguide is respectively and electrically connected with the first ground wire and the signal wire; the projection of the second section of PN junction silicon optical waveguide on the traveling wave electrode is positioned between a signal line and a second ground of the second section of traveling wave electrode, and the PN junction of the second section of PN junction silicon optical waveguide is electrically connected with the signal line and the second ground respectively; and the signal line of the traveling wave electrode is respectively and electrically connected with the P-type semiconductor of the first section of PN junction silicon optical waveguide and the P-type semiconductor of the second section of PN junction silicon optical waveguide, or the signal line is respectively and electrically connected with the N-type semiconductor of the first section of PN junction silicon optical waveguide and the N-type semiconductor of the second section of PN junction silicon optical waveguide. Through the design of the bent GSG traveling wave electrode and the bent silicon optical waveguide, the first section of PN junction silicon optical waveguide is electrically connected with a first ground wire and a signal wire of the first section of traveling wave electrode and is far away from a second ground wire of the first section of traveling wave electrode, so that the first section of PN junction silicon optical waveguide is inclined to the right on the first section of traveling wave electrode; the second section of PN junction silicon optical waveguide is electrically connected with the signal line and the second ground wire of the second section of traveling wave electrode and is far away from the first ground wire of the second section of traveling wave electrode, so that the second section of PN junction silicon optical waveguide is deviated to the left on the second section of traveling wave electrode, a bilaterally symmetrical structure is formed on the traveling wave electrode in one period, an equivalent symmetrical PN junction load can be realized, the generation of a high-order radio frequency mode is effectively inhibited, and the signal transmission quality is improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

In order to more clearly explain the technical solution of the present application, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious to those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of a connection relationship of an optical communication terminal;

fig. 2 is a schematic structural diagram of an optical network terminal;

fig. 3 is a schematic structural diagram of an optical module according to an embodiment of the present application;

fig. 4 is an exploded schematic structural diagram of an optical module according to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of the connection of a traveling wave electrode to a silicon optical waveguide of an exemplary conventional linear silicon optical modulator;

FIG. 6 is a schematic diagram of a partial connection of a traveling wave electrode to a silicon optical waveguide of an exemplary conventional linear silicon optical modulator;

FIG. 7 is a schematic diagram of a bandwidth test curve for an exemplary conventional linear silicon optical modulator;

FIG. 8 is an eye diagram of an exemplary conventional linear silicon light modulator;

FIG. 9 is a schematic diagram of the connection between the traveling-wave electrode and the silicon optical waveguide of the silicon optical modulator in the embodiment of the present application;

FIG. 10 is a schematic diagram of a partial connection between a traveling-wave electrode and a silicon optical waveguide of a silicon optical modulator according to an embodiment of the present application;

FIG. 11 is a schematic diagram of the connection between the traveling wave electrode and the silicon optical waveguide with PN junction in the embodiment of the present application;

FIG. 12 is a schematic diagram of a bandwidth test curve of a silicon optical modulator in an embodiment of the present application;

fig. 13 is an eye diagram of a silicon optical modulator in an embodiment of the present application.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

One of the core links of optical fiber communication is the interconversion of optical and electrical signals. The optical fiber communication uses optical signals carrying information to transmit in information transmission equipment such as optical fibers/optical waveguides, and the information transmission with low cost and low loss can be realized by using the passive transmission characteristic of light in the optical fibers/optical waveguides; meanwhile, the information processing device such as a computer uses an electric signal, and in order to establish information connection between the information transmission device such as an optical fiber or an optical waveguide and the information processing device such as a computer, it is necessary to perform interconversion between the electric signal and the optical signal.

The optical module realizes the function of interconversion of optical signals and electrical signals in the technical field of optical fiber communication, and the interconversion of the optical signals and the electrical signals is the core function of the optical module. The optical module is electrically connected with an external upper computer through a golden finger on an internal circuit board of the optical module, and the main electrical connection comprises power supply, I2C signals, data information, grounding and the like; the electrical connection mode realized by the gold finger has become the mainstream connection mode of the optical module industry, and on the basis of the mainstream connection mode, the definition of the pin on the gold finger forms various industry protocols/specifications.

Fig. 1 is a schematic diagram of connection relationship of an optical communication terminal. As shown in fig. 1, the connection of the optical communication terminal mainly includes interconnection among the optical network terminal 100, the optical module 200, the optical fiber 101, and the network cable 103.

One end of the optical fiber 101 is connected with a far-end server, one end of the network cable 103 is connected with local information processing equipment, and the connection between the local information processing equipment and the far-end server is completed by the connection between the optical fiber 101 and the network cable 103; and the connection between the optical fiber 101 and the network cable 103 is made by the optical network terminal 100 having the optical module 200.

An optical port of the optical module 200 is externally accessed to the optical fiber 101, and establishes bidirectional optical signal connection with the optical fiber 101; an electrical port of the optical module 200 is externally connected to the optical network terminal 100, and establishes bidirectional electrical signal connection with the optical network terminal 100; the optical module realizes the mutual conversion of optical signals and electric signals, thereby realizing the establishment of information connection between the optical fiber and the optical network terminal. Specifically, the optical signal from the optical fiber is converted into an electrical signal by the optical module and then input to the optical network terminal 100, and the electrical signal from the optical network terminal 100 is converted into an optical signal by the optical module and input to the optical fiber.

The optical network terminal is provided with an optical module interface 102, which is used for accessing an optical module 200 and establishing bidirectional electric signal connection with the optical module 200; the optical network terminal is provided with a network cable interface 104, which is used for accessing the network cable 103 and establishing bidirectional electric signal connection with the network cable 103; the optical module 200 is connected to the network cable 103 via the optical network terminal 100. Specifically, the optical network terminal transmits a signal from the optical module to the network cable and transmits the signal from the network cable to the optical module, and the optical network terminal serves as an upper computer of the optical module to monitor the operation of the optical module.

At this point, a bidirectional signal transmission channel is established between the remote server and the local information processing device through the optical fiber, the optical module, the optical network terminal and the network cable.

Common information processing apparatuses include routers, switches, electronic computers, and the like; the optical network terminal is an upper computer of the optical module, provides data signals for the optical module, and receives the data signals from the optical module, and the common upper computer of the optical module also comprises an optical line terminal and the like.

Fig. 2 is a schematic diagram of an optical network terminal structure. As shown in fig. 2, the optical network terminal 100 has a circuit board 105, and a cage 106 is disposed on a surface of the circuit board 105; an electric connector is arranged in the cage 106 and used for connecting an electric port of an optical module such as a golden finger; the cage 106 is provided with a heat sink 107, and the heat sink 107 has a projection such as a fin that increases a heat radiation area.

The optical module 200 is inserted into the optical network terminal 100, specifically, an electrical port of the optical module is inserted into an electrical connector inside the cage 106, and an optical port of the optical module is connected to the optical fiber 101.

The cage 106 is positioned on the circuit board, and the electrical connector on the circuit board is wrapped in the cage, so that the electrical connector is arranged in the cage; the optical module is inserted into the cage, held by the cage, and the heat generated by the optical module is conducted to the cage 106 and then diffused by the heat sink 107 on the cage.

Fig. 3 is a schematic view of an optical module according to an embodiment of the present disclosure, and fig. 4 is a schematic view of an exploded structure of an optical module according to an embodiment of the present disclosure. As shown in fig. 3 and 4, the optical module 200 provided in the embodiment of the present application includes an upper housing 201, a lower housing 202, an unlocking member 203, a circuit board 300, a silicon optical chip 400, a light source 500, and an optical fiber receptacle 600.

The upper shell 201 is covered on the lower shell 202 to form a wrapping cavity with two openings; the outer contour of the packaging cavity generally presents a square body. Specifically, the lower housing 202 includes a main board and two side boards located at two sides of the main board and arranged perpendicular to the main board; the upper shell comprises a cover plate, and the cover plate covers two side plates of the upper shell to form a wrapping cavity; the upper shell may further include two side walls disposed at two sides of the cover plate and perpendicular to the cover plate, and the two side walls are combined with the two side plates to cover the upper shell 201 on the lower shell 202.

The two openings can be two end openings (204, 205) located at the same end of the optical module, or two openings located at different ends of the optical module; one opening is an electric port 204, and a gold finger of the circuit board extends out of the electric port 204 and is inserted into an upper computer such as an optical network terminal; the other opening is an optical port 205 for external optical fiber access to connect the silicon optical chip 400 inside the optical module; the photoelectric devices such as the circuit board 300, the silicon optical chip 400, the light source 500 and the like are positioned in the packaging cavity.

The assembly mode of combining the upper shell and the lower shell is adopted, so that the circuit board 300, the silicon optical chip 400 and other devices can be conveniently installed in the shells, and the upper shell and the lower shell form the outermost packaging protection shell of the module; the upper shell and the lower shell are made of metal materials generally, electromagnetic shielding and heat dissipation are achieved, the shell of the optical module cannot be made into an integral component generally, and therefore when devices such as a circuit board are assembled, the positioning component, the heat dissipation component and the electromagnetic shielding component cannot be installed, and production automation is not facilitated.

The unlocking component 203 is located on the outer wall of the wrapping cavity/lower shell 202, and is used for realizing the fixed connection between the optical module and the upper computer or releasing the fixed connection between the optical module and the upper computer.

The unlocking component 203 is provided with a clamping component matched with the upper computer cage; the end of the unlocking component can be pulled to enable the unlocking component to move relatively on the surface of the outer wall; the optical module is inserted into a cage of the upper computer, and the optical module is fixed in the cage of the upper computer by a clamping component of the unlocking component; by pulling the unlocking component, the clamping component of the unlocking component moves along with the unlocking component, so that the connection relation between the clamping component and the upper computer is changed, the clamping relation between the optical module and the upper computer is released, and the optical module can be drawn out from the cage of the upper computer.

The circuit board 300 is provided with circuit traces, electronic components (such as capacitors, resistors, triodes, and MOS transistors), and chips (such as an MCU, a laser driver chip, a limiting amplifier chip, a clock data recovery CDR, a power management chip, and a data processing chip DSP).

The circuit board 300 connects the electrical devices in the optical module together according to the circuit design through circuit wiring to realize the electrical functions of power supply, electrical signal transmission, grounding and the like.

The circuit board is generally a hard circuit board, and the hard circuit board can also realize a bearing effect due to the relatively hard material of the hard circuit board, for example, the hard circuit board can stably bear a chip; when the optical transceiver component is positioned on the circuit board, the rigid circuit board can also provide stable bearing; the hard circuit board can also be inserted into an electric connector in the upper computer cage, and specifically, a metal pin/golden finger is formed on the surface of the tail end of one side of the hard circuit board and is used for being connected with the electric connector; these are not easily implemented with flexible circuit boards.

A flexible circuit board is also used in a part of the optical module to supplement a rigid circuit board; the flexible circuit board is generally used in combination with a rigid circuit board, for example, the rigid circuit board may be connected to the optical transceiver module by using the flexible circuit board.

The silicon optical chip 400 is arranged on the circuit board 300 and electrically connected with the circuit board 300, and specifically can be wire bonding connection; the periphery of the silicon optical chip 400 is connected to the circuit board 300 via a plurality of conductive wires, so the silicon optical chip 400 is generally disposed on the surface of the circuit board 300.

In this example, the light source 500 may be a laser box, the silicon optical chip 400 and the laser box are optically connected through a first optical fiber ribbon 401, and the silicon optical chip 400 receives light from the laser box through the first optical fiber ribbon 401, so as to modulate the light, specifically, load a signal onto the light; the silicon optical chip 400 receives light from the fiber optic receptacle 600, and converts the optical signal into an electrical signal.

The silicon optical chip 400 and the optical fiber receptacle 600 are optically connected through the second optical fiber ribbon 402, and the optical fiber receptacle 600 is optically connected to an optical fiber outside the optical module. The light modulated by the silicon optical chip 400 is transmitted to the optical fiber socket 600 through the second optical fiber ribbon 402 and transmitted to the external optical fiber through the optical fiber socket 600; light transmitted from the external optical fiber is transmitted to the second optical fiber ribbon 402 through the optical fiber socket 600, and is transmitted to the silicon optical chip 400 through the second optical fiber ribbon 402, so that the silicon optical chip 400 outputs light carrying data to the external optical fiber of the optical module, or receives light carrying data from the external optical fiber of the optical module.

To accomplish the modulation of light, silicon optical chip 400 includes a silicon optical modulator, which includes an optical splitter, a first interference arm, a second interference arm, and an optical combiner, the input end of the optical splitter being optically connected to first optical fiber ribbon 401 for receiving light from the laser box; the first output end of the optical splitter is connected with one end of the first interference arm, the second output end of the optical splitter is connected with one end of the second interference arm, and the optical splitter divides the received light into two parts which are respectively transmitted to the first interference arm and the second interference arm; the first interference arm and the second interference arm respectively modulate input light and modulate light which does not carry signals into signal light; the other end of the first interference arm is connected with a first input end of the light combiner, the other end of the second interference arm is connected with a second input end of the light combiner, and the light combiner combines signal light output by the first interference arm and the second interference arm, so that signals are loaded onto the light.

In this example, the silicon optical chip 400 is provided with an input optical port and an output optical port, the input optical port is used for coupling the light output by the laser box into the silicon optical chip 400, and the output optical port is used for coupling the modulated signal out of the silicon optical chip 400, so that the silicon optical modulator is used for realizing optical modulation and photoelectric response.

Fig. 5 is a schematic diagram showing the connection between the traveling wave electrode and the silicon optical waveguide of the conventional linear silicon optical modulator, and fig. 6 is a schematic diagram showing the local connection between the traveling wave electrode and the silicon optical waveguide of the conventional linear silicon optical modulator. As shown in fig. 5 and 6, the conventional silicon optical modulator adopts a linear traveling wave electrode design to realize high-speed electro-optical modulation, the commonly used traveling wave electrode adopts a coplanar waveguide type transmission line GSG structure, S is a signal line and is positioned in the middle, and G is a ground line and is positioned at two sides of the S signal line; the silicon optical waveguide 403 forms a PN junction by doping, and realizes electro-optic response as a load of the GSG traveling wave electrode. The silicon optical waveguide prepared into the PN junction is generally a linear optical waveguide, and therefore can be connected with only one group of GS signal lines, while the other path of G ground line is in a suspended state, for example, the silicon optical waveguide 403 with the PN junction is arranged between the first ground line G1 and the signal line S, and is respectively connected with the first ground line G1 and the signal line S to realize signal transmission, while the second ground line G2 is in a suspended state, which causes asymmetry of the whole system, and results in that the GSG traveling wave electrode generates a high-order radio frequency mode, which affects the signal transmission quality. As shown in fig. 7, in the bandwidth test curve, there is a significant loss at 15 GHz. As shown in fig. 8, in the eye test, a double line problem appears.

In order to solve the above problem, an embodiment of the present application provides an optical module, where both a GSG traveling wave electrode and a silicon optical waveguide in a silicon optical modulator of the optical module adopt a bending design, and the silicon optical waveguide and the GSG traveling wave electrode are designed in a crossed manner, and an equivalent symmetric PN junction load can be implemented within a whole device length range, so as to effectively suppress generation of a high-order radio frequency mode and improve signal transmission quality.

Fig. 9 is a schematic connection diagram of a traveling-wave electrode and a silicon optical waveguide in a silicon optical modulator according to an embodiment of the present application, and fig. 10 is a schematic connection diagram of a portion of the traveling-wave electrode and the silicon optical waveguide in the silicon optical modulator according to the embodiment of the present application. As shown in fig. 9 and 10, the first interference arm and the second interference arm of the silicon optical modulator each include a traveling wave electrode disposed in a bent manner and a silicon optical waveguide disposed in a bent manner, and a projection of the silicon optical waveguide on the traveling wave electrode is located between a ground line and a signal line of the traveling wave electrode. The bending type traveling wave electrode comprises a first section of traveling wave electrode 404, a bending section of traveling wave electrode 405 and a second section of traveling wave electrode 406 which are integrally connected, and the first section of traveling wave electrode 404 and the second section of traveling wave electrode 406 are symmetrically arranged.

The traveling wave electrode adopts a coplanar waveguide type transmission line GSG structure, so that a first ground wire G1 of the traveling wave electrode comprises a first running line segment, a second running line segment and a first arc-shaped running line segment which are integrally connected, and the first arc-shaped running line segment is connected with the first running line segment and the second running line segment; the signal wire S comprises a third wire segment, a fourth wire segment and a second arc-shaped wire segment which are integrally connected, and the second arc-shaped wire segment is connected with the third wire segment and the fourth wire segment; the second ground comprises a fifth route segment, a sixth route segment and a third arc route segment which are integrally connected, and the third arc route segment is connected with the fifth route segment and the sixth route segment.

In this example, the first section of traveling-wave electrode 404 and the second section of traveling-wave electrode 406 may both be straight section traveling-wave electrodes, and the first section of traveling-wave electrode 404 and the second section of traveling-wave electrode 406 are symmetrically disposed about a central axis of the bent section of traveling-wave electrode 405. Specifically, the first section of traveling-wave electrode 404 and the second section of traveling-wave electrode 406 may both be parallel to the central axis of the bent section of traveling-wave electrode 405, and the bent section of traveling-wave electrode 405 is a semicircular traveling-wave electrode. Namely, the first section of traveling wave electrode 404 and the second section of traveling wave electrode 406 are horizontally arranged, and the traveling wave electrode in one period is in a U-shaped structure.

The first section of traveling wave electrode 404 and the second section of traveling wave electrode 406 may also be both disposed at a predetermined angle with respect to the central axis of the bent section of traveling wave electrode 405, and the bent section of traveling wave electrode 405 is an arc-shaped traveling wave electrode. That is, the first section of traveling wave electrode 404 and the second section of traveling wave electrode 406 are arranged obliquely, and an appropriate angle can be selected according to the actual situation of the optical module.

When the traveling wave electrode is a bent GSG traveling wave electrode, the first ground G1, the signal line S, and the second ground G2 of the first stage traveling wave electrode 404 are disposed corresponding to the first ground G1, the signal line S, and the second ground G2 of the second stage traveling wave electrode 406, and if the first ground G1, the signal line S, and the second ground G2 of the first stage traveling wave electrode 404 are sequentially arranged from top to bottom, the first ground G1, the signal line S, and the second ground G2 of the second stage traveling wave electrode 406 are sequentially arranged from bottom to top, and the first ground G1, the signal line S, and the second ground G2 of the bent stage traveling wave electrode 405 are sequentially arranged from outside to inside, that is, the first ground G1 is located outside the traveling wave electrode, and the second ground G2 is located inside the traveling wave electrode.

The silicon optical waveguide comprises a first section of PN junction silicon optical waveguide 408, a bent section of silicon optical waveguide 407 and a second section of PN junction silicon optical waveguide 409, namely, the first section of silicon optical waveguide arranged below the first section of traveling wave electrode 404 comprises a first PN junction formed by different doped regions, only the silicon optical waveguide arranged below the bent section of traveling wave electrode 405 is not doped with the PN junction, and the second section of silicon optical waveguide arranged below the second section of traveling wave electrode 406 comprises a second PN junction formed by different doped regions. Specifically, the projection of the first section of PN junction silicon optical waveguide 408 on the first section of traveling-wave electrode 404 is located between the first ground line G1 and the signal line S of the first section of traveling-wave electrode 404, and is electrically connected to the first ground line G1 and the signal line S of the first section of traveling-wave electrode 404, that is, the projection of the first section of PN junction silicon optical waveguide 408 on the first section of traveling-wave electrode 404 is located between the first route section of the first ground line G1 and the third route section of the signal line S, and is electrically connected to the first route section and the third route section, respectively. Thus, the first PN junction is offset from the second ground G2 of the first section traveling wave electrode 404, and the first section PN junction silicon optical waveguide 408 is offset to the right on the first section traveling wave electrode 404; the projection of the second section of the PN junction silicon optical waveguide 409 on the second section of the traveling-wave electrode 406 is located between the signal line S of the second section of the traveling-wave electrode 406 and the second ground G2, and is electrically connected with the signal line S of the second section of the traveling-wave electrode 406 and the second ground G2, that is, the projection of the second section of the PN junction silicon optical waveguide 409 on the second section of the traveling-wave electrode 406 is located between the fourth wiring section of the signal line S and the sixth wiring section of the second ground G2, and is electrically connected with the fourth wiring section and the sixth wiring section, respectively. Thus, the second PN junction deviates from the first ground line G1 of the second section of the traveling-wave electrode 406, and the second section of the PN junction silicon optical waveguide 409 deviates to the left on the second section of the traveling-wave electrode 406, so that a bilaterally symmetrical structure is formed on the traveling-wave electrode of one period, an equivalent symmetrical PN junction load is realized, and electro-optic response is realized as the load of the GSG traveling-wave electrode.

The top layer metal of the traveling wave electrode adopts a GSG form, the top layer metal is connected with the PN junction through the through hole, namely the inside of the through hole is also filled with metal, the upper surface of the through hole metal is contacted with the GSG metal electrode pattern layer, and the lower surface of the through hole metal is contacted with the PN junction silicon optical waveguide, so that the whole signal transmission process is that a GSG radio frequency signal is connected with the PN junction silicon optical waveguide through the metal through hole, and the connection attribute is resistance connection.

The traveling wave electrode adopts a silicon substrate (SOI substrate) on an insulator, and a light waveguide structure is etched on the substrate and correspondingly doped to form a P-N structure; depositing a layer of SiO₂Forming an upper limiting layer of the optical waveguide and serving as an isolating layer of the positive electrode and the negative electrode; secondly, etching a lead hole to provide a path for electrically connecting the metal and the PN junction silicon optical waveguide; and finally, depositing a metal layer, filling the lead holes and covering the upper surface of the chip, and etching according to the designed GSG metal electrode pattern to finally form a traveling wave electrode structure.

Fig. 11 is a schematic electrical connection diagram of a traveling-wave electrode and a silicon optical waveguide in a silicon optical modulator according to an embodiment of the present application. As shown in fig. 11, the PN junction is formed by an N-type doped region and a P-type doped region in close contact, i.e., on a complete silicon wafer, an N-type semiconductor is formed on one side and a P-type semiconductor is formed on the other side by different doping processes, and the region near the interface between the P-type semiconductor and the N-type semiconductor is the PN junction.

The PN junction generally includes a central waveguide region, a P-type semiconductor and an N-type semiconductor, and the P-type semiconductor or the N-type semiconductor is connected to a signal line or a ground line of the traveling wave electrode as a load of the GSG traveling wave electrode. Specifically, the P-type semiconductor of the first section of PN junction silicon optical waveguide 408 is electrically connected to the signal line S of the first section of traveling-wave electrode 404, the N-type semiconductor is electrically connected to the first ground line G1 of the first section of traveling-wave electrode 404, the P-type semiconductor of the second section of PN junction silicon optical waveguide 409 is electrically connected to the signal line S of the second section of traveling-wave electrode 406, and the N-type semiconductor is electrically connected to the second ground line G2 of the second section of traveling-wave electrode 406; alternatively, the P-type semiconductor of the first PN junction silicon optical waveguide 408 is electrically connected to the first ground line G1 of the first traveling wave electrode 404, the N-type semiconductor is electrically connected to the signal line S of the first traveling wave electrode 404, the P-type semiconductor of the second PN junction silicon optical waveguide 409 is electrically connected to the second ground line G2 of the second traveling wave electrode 406, and the N-type semiconductor is electrically connected to the signal line S of the second traveling wave electrode 406. That is, the third wire segment of the signal line S is electrically connected to the P-type semiconductor of the first PN junction silicon optical waveguide 408, the fourth wire segment is electrically connected to the P-type semiconductor of the second PN junction silicon optical waveguide 409, or the third wire segment of the signal line S is electrically connected to the N-type semiconductor of the first PN junction silicon optical waveguide 408, and the fourth wire segment is electrically connected to the N-type semiconductor of the second PN junction silicon optical waveguide 409. Therefore, the two sections of silicon optical waveguides prepared into the PN junction are arranged in a crossed mode with the GSG traveling wave electrode, equivalent symmetrical PN junction load can be achieved, generation of a high-order radio frequency mode can be effectively restrained, and signal transmission quality is improved.

After the P-type semiconductor and the N-type semiconductor are combined, because the free electrons in the N-type region are majority electrons and the holes are almost zero, the holes are called minority electrons, and the holes in the P-type region are majority electrons and the free electrons are minority electrons, the concentration difference of the electrons and the holes is generated at the junction of the P-type semiconductor and the N-type semiconductor. Due to the difference in free electron and hole concentration, some electrons diffuse from the N-type region to the P-type region, and some holes also diffuse from the P-type region to the N-type region. As a result of their diffusion, the P region loses holes and leaves negatively charged impurity ions, and the N region loses electrons and leaves positively charged impurity ions. Ions in the semiconductor cannot move arbitrarily in open circuits and therefore do not participate in conduction. These immobile charged particles form a space charge region near the interface of the P and N regions, the thickness of which is related to the dopant concentration.

After the space charge region is formed, an internal electric field is formed in the space charge region in a direction from the positively charged N region to the negatively charged P region due to the interaction between the positive and negative charges. Obviously, the direction of this electric field is opposite to the direction of the carrier diffusion motion, preventing diffusion.

On the other hand, this electric field will cause minority carrier holes in the N region to drift towards the P region and minority carrier electrons in the P region to drift towards the N region, with the direction of drift motion being exactly opposite to the direction of diffusion motion. The holes drifting from the N region to the P region supplement the holes lost by the P region on the original interface, and the electrons drifting from the P region to the N region supplement the electrons lost by the N region on the original interface, so that the space charge is reduced, and the internal electric field is weakened. Therefore, as a result of the drift motion, the space charge region is narrowed and the diffusion motion is enhanced.

Finally, the diffusion of majority carriers and the drift of minority carriers reach dynamic equilibrium. On both sides of the junction surface of the P-type semiconductor and the N-type semiconductor, there are ion thin layers, and a space charge region formed by the ion thin layers is called a PN junction.

The PN junction of the first section of PN junction silicon optical waveguide 408 is electrically connected with the first ground wire G1 and the signal wire S of the first section of traveling wave electrode 404, the PN junction of the second section of PN junction silicon optical waveguide 409 is electrically connected with the signal wire S and the second ground wire G2 of the second section of traveling wave electrode 406, so that the change of the voltage at the two ends of the PN junction can cause the change of the width of the depletion region of the PN junction, the change of the width of the depletion region of the PN junction can cause the change of the refractive index distribution of the silicon optical waveguide, the change of the refractive index distribution of the silicon optical waveguide can cause the change of the mode field of electromagnetic waves therein, and further the change of the transmitted electromagnetic waves can be caused, thereby realizing the electro-optical modulation function of the silicon optical modulator.

In this example, the lengths of the first PN junction silicon optical waveguide 408 and the second PN junction silicon optical waveguide 409 are the same, that is, the length of the first PN junction silicon optical waveguide 408 in the first traveling wave electrode 404 is the same as the length of the second PN junction silicon optical waveguide 409 in the second traveling wave electrode 406, so as to ensure that the first PN junction silicon optical waveguide 408 and the second PN junction silicon optical waveguide 409 are symmetrically arranged.

In addition, the number of PN junctions in the first section of PN junction silicon optical waveguide 408 and the second section of PN junction silicon optical waveguide 409 are the same, so that a pair of symmetrical PN junctions are formed by the PN junctions in the first section of PN junction silicon optical waveguide 408 and the PN junctions in the second section of PN junction silicon optical waveguide 409, a single PN junction cannot appear, and thus, the travelling wave electrode and the silicon optical waveguide are further ensured to form equivalent symmetrical PN junction loads.

In this example, the interference arm of the silicon optical modulator may include only the first section of traveling-wave electrode 404, the bent section of traveling-wave electrode 405, and the second section of traveling-wave electrode 406, i.e. only one bending period of traveling-wave electrode; it can also be made up of the first stage traveling wave electrode 404, the bending stage traveling wave electrode 405 and the second stage traveling wave electrode 406 to form a periodic traveling wave electrode, the interference arm of the silicon optical modulator includes a plurality of periodic traveling wave electrodes, that is, the traveling wave electrode is arranged in a periodic bending way.

The silicon optical waveguide is arranged between the ground wire and the signal wire of the traveling wave electrode, so the silicon optical waveguide can only comprise a first section of PN junction silicon optical waveguide 408, a bent section of silicon optical waveguide 407 and a second section of PN junction silicon optical waveguide 409; the silicon optical waveguide with one period can also be formed by the first section of PN junction silicon optical waveguide 408, the bent section of silicon optical waveguide 407 and the second section of PN junction silicon optical waveguide 409, and the interference arm of the silicon optical modulator comprises a plurality of periods of silicon optical waveguides, so that equivalent symmetrical PN junction load can be realized in the whole device length range.

When the silicon optical modulator includes the traveling wave electrode that is periodically bent, two ends of the first section of traveling wave electrode 404 are respectively connected to the bent section of traveling wave electrode 405, and two ends of the second section of traveling wave electrode 406 are respectively connected to the bent section of traveling wave electrode 405. And the traveling wave electrode of the interference arm comprises at least one periodic traveling wave electrode which is arranged in a bending way, and equivalent symmetrical PN junction load is realized in the length range of the whole device through the crossed design of the silicon optical waveguide and the GSG traveling wave electrode.

When the silicon optical modulator comprises a silicon optical waveguide which is periodically bent, two ends of the first section of PN junction silicon optical waveguide 408 are respectively connected with the bent section of silicon optical waveguide 407, two ends of the second section of PN junction silicon optical waveguide 409 are respectively connected with the bent section of silicon optical waveguide 407, and the silicon optical waveguide of the interference arm comprises at least one period of silicon optical waveguide which is bent.

In this example, since the first interference arm and the second interference arm of the silicon optical modulator are symmetrically arranged, the traveling wave electrodes of the first interference arm and the second interference arm are also symmetrically arranged, the input end of the first interference arm and the input end of the second interference arm share the second ground G2, and the output end of the first interference arm and the output end of the second interference arm share the second ground G2, so that an equivalent symmetrical PN junction load can be realized within the whole length range of the silicon optical modulator, the generation of a high-order radio frequency mode can be effectively suppressed, and the signal transmission quality can be improved.

Through the design of the bent GSG traveling wave electrode and the bent silicon optical waveguide, and the silicon optical waveguide and the GSG traveling wave electrode are arranged in a crossed manner in a period, in one period, the silicon optical waveguide prepared into the PN junction can be connected with a group of first ground wires G1 and a signal wire S, can also be connected with a group of signal wires S and a second ground wire G2, and cannot cause one path of ground wires G to be in a suspension state, so that an equivalent symmetrical PN junction load is realized, the generation of a high-order radio frequency mode is effectively inhibited, and the signal transmission quality is improved. As shown in fig. 12, it can be seen from the bandwidth test curve that the loss at 15GHz is significantly suppressed, and the bandwidth curve is very smooth; as shown in fig. 13, in the eye test, the double line problem was solved, and the eye quality was good.

In this example, the traveling wave electrode and the silicon optical waveguide arranged in a curved manner in the silicon optical modulator can not only improve the signal transmission quality, but also reduce the overall length of the silicon optical modulator. If the silicon optical modulator adopts a linear traveling wave electrode, the effective length is 2 mm; when the silicon optical modulator adopts the bending type traveling wave electrode, the effective length reaches 2.8mm, and the whole length of the silicon optical modulator is reduced by nearly 1mm compared with that of the linear type traveling wave electrode, so that the whole volume of the silicon optical modulator can be reduced.

When the silicon optical modulator adopts the bending traveling wave electrode, the structures of all devices in the silicon optical modulator are compact, and the ultra-compact silicon optical modulator is very suitable for application scenes needing ultra-small packaging, such as a single-channel 25G Tunable TOSA product, and is beneficial to the miniaturization of an optical module.

The optical module provided by the embodiment of the application comprises a circuit board, a light source and a silicon optical chip, wherein the silicon optical chip comprises a silicon optical modulator, the silicon optical modulator comprises a first interference arm and a second interference arm which are symmetrically arranged, the first interference arm and the second interference arm respectively comprise a traveling wave electrode which is arranged in a bent mode and a silicon optical waveguide which is arranged in a bent mode, and the projection of the silicon optical waveguide on the traveling wave electrode is located between the ground wire and the signal wire of the traveling wave electrode; the traveling wave electrode adopts a coplanar waveguide structure and comprises a first section of traveling wave electrode, a bent section of traveling wave electrode and a second section of traveling wave electrode which are integrally connected, wherein the first section of traveling wave electrode and the second section of traveling wave electrode are symmetrically arranged; the silicon optical waveguide comprises a first section of PN junction silicon optical waveguide, a bent section of silicon optical waveguide and a second section of PN junction silicon optical waveguide, the projection of the first section of PN junction silicon optical waveguide on the first section of traveling wave electrode is positioned between a first ground wire and a signal wire of the first section of traveling wave electrode, the PN junction of the first section of PN junction silicon optical waveguide is respectively and electrically connected with the first ground wire and the signal wire, the projection of the second section of PN junction silicon optical waveguide on the second section of traveling wave electrode is positioned between the signal wire and a second ground wire of the second section of traveling wave electrode, the PN junction of the second section of PN junction silicon optical waveguide is respectively and electrically connected with the signal wire and the second ground wire, and the signal line of the traveling wave electrode is respectively and electrically connected with the P-type semiconductor of the first section of PN junction silicon optical waveguide and the P-type semiconductor of the second section of PN junction silicon optical waveguide, or the signal wire of the traveling wave electrode is respectively and electrically connected with the N-type semiconductor of the first section of PN junction silicon optical waveguide and the N-type semiconductor of the second section of PN junction silicon optical waveguide. The silicon optical waveguide with the PN junction prepared in the way can be connected with a first ground wire and a signal wire of the traveling wave electrode and can also be connected with a second ground wire and a signal wire of the traveling wave electrode, an equivalent symmetrical PN junction load is realized within the length range of the whole device, the generation of a high-order radio frequency mode is effectively inhibited, and the signal transmission quality is improved. In addition, the traveling wave electrode arranged in a bending mode can reduce the volume of the silicon optical modulator, and is very suitable for an optical module needing subminiature packaging.

It should be noted that, in the present specification, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such circuit structure, article, or apparatus. Without further limitation, the presence of an element identified by the phrase "comprising an … …" does not exclude the presence of other like elements in a circuit structure, article or device comprising the element.

Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

The above-described embodiments of the present application do not limit the scope of the present application.

Claims

1. A light module, comprising:

a circuit board;

2. The optical module according to claim 1, wherein the first section of traveling-wave electrode, the bent section of traveling-wave electrode, and the second section of traveling-wave electrode constitute a periodic traveling-wave electrode, and the first interference arm and the second interference arm include a plurality of periodic traveling-wave electrodes.

3. The optical module of claim 2, wherein two ends of the first section of the PN junction silicon optical waveguide are respectively connected to the curved section of the silicon optical waveguide, and two ends of the second section of the PN junction silicon optical waveguide are respectively connected to the curved section of the silicon optical waveguide.

4. The optical module of claim 1, wherein the first section of traveling wave electrode and the second section of traveling wave electrode are both straight section traveling wave electrodes.

5. The optical module according to claim 4, wherein the first section of traveling wave electrode and the second section of traveling wave electrode are both parallel to a central axis of the curved section of traveling wave electrode, and the curved section of traveling wave electrode is a semicircular traveling wave electrode.

6. The optical module according to claim 4, wherein the first end traveling wave electrode and the second end traveling wave electrode are both disposed at a predetermined angle with respect to a central axis of the bent section traveling wave electrode.

7. The optical module of claim 1, wherein the first segment of the PN junction silicon optical waveguide and the second segment of the PN junction silicon optical waveguide have the same length.

8. The optical module of claim 1, wherein the number of PN junctions in the first segment of the PN junction silicon optical waveguide is the same as the number of PN junctions in the second segment of the PN junction silicon optical waveguide.

9. The optical module of claim 1, wherein the interference arm comprises a first interference arm and a second interference arm, and an input end of the first interference arm and an input end of the second interference arm share a second ground.

10. The optical module of claim 9, wherein the output end of the first interference arm and the output end of the second interference arm share a second ground.